Phase lock loop is indispensable in a pulse generator. The phase lock loop, capable of precisely controlling pulse or frequency, can be used in frequency modulation for wireless signals or clock control for digital products to simplify the complexity and increase the precision of circuit.
In a conventional phase lock loop, an analog lock detector is used to indicate the state of the phase lock loop, that is, whether the phase lock loop is in a lock state or an unlock state. Since the analog lock detector occupies a large circuit area and consumes a large amount of power, the digital lock detector is thus provided. However, neither the analog lock detector nor the digital lock detector precisely defines the lock state.